Active primary batteries are a well known type of primary battery which do not require activation before use. Therefore, their power can be delivered instantly on demand. These batteries are useful in applications requiring low to moderate current densities. They typically operate over a temperature range extending from about -20.degree. C. to +60.degree. C. Shelf life for these batteries is given in years unless storage temperatures become excessively elevated above ambient.
One important class of active primary batteries utilizes a zinc anode, a caustic aqueous electrolyte, and a solid cathode made of manganese dioxide, silver (II) oxide ("AgO"), or mercuric oxide ("HgO"). These batteries generally develop a potential of about 1.5 volts. They have good power density and work over a reasonable temperature range. The packaged volumetric energy density of the zinc-manganese dioxide system is not very high; however, the packaged energy density of the zinc-mercuric oxide system is significantly higher. The packaged volumetric energy density of the zinc-silver (II) oxide system is about twice that of the zinc-manganese dioxide system primarily because of the excellent amp-hr capacity of silver (II) oxide.
A second important class of active primary batteries utilizes a lithium anode, an aprotic organic electrolyte, and a solid cathode made of manganese dioxide. These batteries typically develop a potential of about 3.0 volts. They have good power density and work over a reasonable temperature range. The packaged volumetric energy density of the lithium-manganese dioxide system is about twice that of the zinc manganese-dioxide system primarily because of the high potential developed by the lithium anode.
There is a third class of active primary batteries which are solid state in nature. An example of such an active primary battery is the lithium-iodine battery. It develops a potential of about 2.8 volts and has a packaged volumetric energy density somewhat above that of the zinc-silver (II) oxide and lithium-manganese dioxide couples. However, the lithium-iodine couple can only be used to power low rate devices such as implantable pacemakers and electronic watches.
U.S. Pat. No. 3,853,627 mentions in passing that known cells include those with lithium anodes, non-aqueous electrolytes, and a silver oxide cathode. U.S. Pat. No. 4,167,609 theorizes constructing a battery with a lithium anode, a silver (II) oxide cathode, and a compatible non-aqueous electrolyte but never indicates what nonaqueous electrolyte is compatible with both lithium and silver (II) oxide. U.S. Pat. No. 4,555,454 mentions in passing that one can combine a lithium anode, a silver (II) oxide cathode, and an aqueous or non-aqueous electrolyte to form a battery. None of these patents, however, demonstrate that such a combination is really possible, has been made, or what non-aqueous electrolyte could be used if it was possible.
The first report in the literature on the lithium-silver (II) oxide system in non-aqueous media is described in the Proceedings of the 8th Annual Power Sources Conference, Atlantic City, N.J. May 19-21, 1964. The paper by J. Farrar, R. Keller, and C. J. Mazac describes experiments performed to determine pairs of anodes and cathodes which could be used to provide high energy density in organic electrolytes. The authors concluded that the lithium-silver (II) oxide couple with an electrolyte composed of LiBr in dimethyl sulfoxide did not perform as well as the lithium-manganese dioxide couple.
A second report describing work with the lithium-silver (II) oxide system in non-aqueous media is dated Nov. 1, 1965 and is the final report on U.S. Army Contract #DA-36-039-AMC-03201 and covers the work period from Jul. 1, 1963 to Jun. 30, 1965. It was written by J. Farrar, R. Keller and M. M. Nicholson and concludes that lithium is the preferred anode material, propylene carbonate is the preferred electrolyte solvent, and BrCN, CuCl.sub.2, and CuF.sub.2 are preferred cathode materials. Silver (II) oxide was described as performing poorly even compared to MnO.sub.2 which was not one of the preferred cathode materials tested.
A third report was written by R. Jasinski and published in Electrochemical Power Sources, 6, 28 (1968). The paper reviews progress in the field of high energy density batteries in relation to the goal of developing a system which delivers twice the energy density of the aqueous caustic zinc-silver oxide system. Jasinski provides a list of proposed reaction mechanisms and theoretical energy densities for electrode couples which could meet this goal. He included the lithium-silver (II) oxide couple on this list but never describes a nonaqueous electrolyte for this system. Jasinski also did not include the lithium-silver (II) oxide system in his description of promising systems.
Japanese Patent Application #55-111075 dated Feb. 21, 1979 describes the use of gelled organic electrolytes in lithium batteries using various solid cathodes. Although most of the work was done with other types of cathodes, a brief description of a lithium-silver (II) oxide battery with a gelled gamma-butyrolactone based electrolyte is shown in Table I. Using gamma-butyrolactone as the non-aqueous electrolyte with a lithium anode and silver (II) oxide cathode is not satisfactory because it provides poor discharge and storage results since the gamma-butyrolactone is unstable in this system.
From this review of the literature it can be seen that a useable battery with a lithium anode, a silver (II) oxide and/or mercuric oxide cathode, and a non-aqueous electrolyte has not been made because the experimental results reported in the literature are far inferior to the theoretical parameters which are summarized hereinafter.
The free energy of formation (.DELTA.G.degree.) of AgO, HgO, Li.sub.2 O, and LiI, as taken from the 70th Edition of the Handbook of Chemistry and Physics, are:
______________________________________ Substance .DELTA.G.degree. (kcal/mole) ______________________________________ AgO 3.3 HgO -13.995 Li.sub.2 O -134.13 LiI -64.60 ______________________________________
The probable power generating reactions occurring in the lithium-silver (II) oxide, lithium-mercuric oxide, and lithium-iodine cells, along with the electromotive force, (E.degree.) generated by these reactions, are:
______________________________________ 2Li + AgO .fwdarw. Li.sub.2 O + Ag E.degree. = 2.980 volts 2Li + HgO .fwdarw. Li.sub.2 O + Hg E.degree. = 2.605 volts 2Li + I.sub.2 .fwdarw. 2LiI E.degree. = 2.801 volts ______________________________________
The free energy information allows the calculation of .DELTA.G.degree. for the reactions shown above. Knowledge of .DELTA.G.degree.; n, the number of electrons transferred in the reaction of interest; and F, Faraday's constant; allows calculation of E.degree., the electromotive force, for the reactions shown above using the formula: EQU E.degree.=-.DELTA.G.degree./nF
The volumetric capacity of an electrode material can be calculated from the formula: EQU Amp-hrs/cc=(amp-hrs/eq) (eq/mole) (gms/cc)/(gins/mole)
where amp-hrs/eq is (96,487 coul/eq)/(3,600 coul/amp-hr) and eq/mole is 1 for lithium and 2 for AgO, HgO, and I.sub.2. Density in gms/cc and molecular weight in gms/mole are taken from the 70th Edition of the Handbook of Chemistry and Physics or the 12th Edition of Lange's Handbook of Chemistry and are shown below along with the calculated capacity for lithium, silver oxide, mercuric oxide, and iodine.
______________________________________ Density Mol Weight Capacity Substance eq/mole (gms/cc) (gms/mole) (amp-hrs/cc) ______________________________________ AgO 2 7.44 123.87 3.22 HgO 2 11.14 216.59 2.75 I.sub.2 2 4.93 253.81 1.04 Li 1 0.534 6.94 2.06 ______________________________________
The volumetric energy density for a battery couple, assuming theoretical cathode density, no separator, and no packaging, can be calculated from the equation: EQU watt-hrs/cc=(E.degree.)/{(1/amp-hrs/cc anode)+(1/amp-hrs/cc cathode) }
Solving this equation for the couples of interest provides the data shown in the table below:
______________________________________ Couple Energy Density (watt-hrs/cc) ______________________________________ Li--AgO 3.75 Li--HgO 3.07 Li--I.sub.2 1.94 ______________________________________
Similarly, the gravimetric energy density of the lithium-silver (II) oxide, lithium mercuric oxide, and lithium-iodine couples can be calculated to be 1,153, 0,604, and 0,560 amp-hrs/gm respectively.
This theoretical information, and therefore the attractiveness of devising a useable lithium-silver (II) oxide and/or lithium-mercuric oxide battery is probably why such couples have been mentioned before in the literature. However, prior attempts to develop a commercially viable or vene a workable lithium-silver (II) oxide battery have been unsuccessful for any number or reasons including the improper choice of electrolytes, the use of unacceptable separators, the use of cell components with unacceptably high levels of impurities, and/or an insufficient understanding of cathode characteristics. It would be desirable therefore to provide a workable and commercially viable high energy density lithium-silver (II) oxide and/or lithium-mercuric oxide battery.